Turbine speed control



Feb. 18, 1958 R. J. ANbERsoN ETAL 2,823,635

TURBINE SPEED CONTROL Filed June 22. 1951 a Sheets-Sheet 1 B I 5 7 5 19 A *0 p \x H6 E1 #5 LT? f: Robert I]: Anderson Vic for W Gelziz er I.

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' R. J. ANDERSON ETAL Feb. 18, 1958 TURBINE SPEED CONTROL 3 She e ts-Sheet 2 Filed June 22, 1951 an an 571 5 '17 TU Ts Faber z L]: Anderson Allen E. Lepleg Z 1521755 2 .L am 1'37 1 4 1,50

Feb. 18, 1958 R. J: ANDERSON ETAL TURBINE SPEED CONTROL Filed June 22, 1951 3 Sheets-Sheet 3 Robert (I Anderson VZ'czor W. Genlzez'i Allen E. I Lap-leg a. Zf-L VE United *ltates TURBINE SPEED CONTROL Application June 22, 1951, Serial No. 233,092

' 17 Claims. Cl. 137-29) This invention relates to a control system for a fluid motor such as a turbine, and more specifically, the invention deals with a turbine speed control system arranged for accurate control of the rotary speed of a turbine through control of the inlet fluid flow.

In automatically controlling the rotary speed of a fluid motor, as in any constant speed control system, the major criteria for satisfactory control are sensitivity, accuracy, fast recovery rate in the presence of changing loads and conditions and the lack of fluctuation or hunting in maintaining a control or set speed. Of these criteria probably the most difficult to achieve in practice is the elimination or substantial elimination of hunting without the provision of complicated damping means. Ordinarily, the provision of adequate damping means results in an undesirably low rate of recovery after sudden changes in operational conditions which tend to overspeed or underspeed the fluid motor or turbine.

The turbine speed control system of the present invention is adapted to accurately control the rotational speed of the turbine and has sufficient sensitivity to instantly sense overspeeding or underspeeding in order to quickly return the turbine to the set speed. The system is provided with fast acting mechanism for quickly returning the turbine to the set speed after a fluctuation therefrom due to changing operational conditions. Very much simplified damping or feed back means are provided to substantially eliminate fluctuations above and below set speed, commonly referred to as hunting.

According to the present invention, a speed sensing unit of a centrifugal flyweight type is connected for rotation to a fluid driven turbine which drives a working mechanism such as a pump. The sensing unit includes biasing means for opposing the flyweight induced axial movement of a rotating shaft in response to increased centrifugal force so that the shaft will assume an axial position as determined by'a balancing of the opposed axial forces. A pilot valve is included in the sensing unit and has two fluid ports connected by reference lines or conduits to opposite sides of a control diaphragm in a servomechanism. The control diaphragm is positively connected to a throttle valve in the servomechanism which controls a variable orifice in the fluid supply line to the turbine. A piston in the pilot valve is adapted to alternately connect the ports therein to an ambient pressure outlet when biased from neutral position.

In one of the embodiments of the invention a pair of bleed lines are connected between the fluid supply source lines and the servomechanism on opposite sides of the control diaphragm therein to supply one or both sides of the control diaphragm with high pressure fluid. Restrictions or orifices are provided in the bleed line. to induce a pressure drop in response to fluid flow in the line for reducing the pressure on one side of the control diaphragm when that side is open to ambient pressure through the pilot valve. This moves the variable orifice in theservomechanism toward open or closed position, depending on which way the throttle valve is moved, in order to comlice pensate for overspeeding or underspeeding of the turbine as detected by the sensing mechanism.

in the other embodiment of the invention one bleed line is connected between the fluid supply source line and the pilot valve in a manner such that supply line pressure is referenced through one port to one side of the servomechanism diaphragm when the other side is referenced to ambient pressure in order to accomplish the same result.

For damping oscillations or hunting about the set turbine speed, damping means are provided in the form of a damping diaphragm in the servomechanism operatively connected to the throttle valve with one side of the damping diaphragm referenced to the pressure upstream of the turbine and with the other side referenced to ambient pressure. There is substantially no time lag in the operation of the damping means so that changes instituted by the speed sensitive unit will be fed back almost instantaneously to prevent overshooting or undershooting. During substantial changes in operating conditions such as with the removal or addition of a heavy load, the

' damping diaphragm damps the operation of the control diaphragm to prevent large oscillatory changes about the set speed to insure a positive and accurate return to said set speed.

v The control system accurately compensates for variations in inlet fluid density as evidenced by the inlet pressure and temperature and also accurately compensates for changes in turbine loading. The speed sensing unit is constructed to have a minimum of inherent hysteresis to allow maximum sensitivity and accuracy of control.

Particularly eflicient means are provided for translating a portion of the centrifugal force acting on the flyweights into axial movement of the pilot valve so that the need for a rotating seal betwen the flyweight portion and the pilot valve is eliminated. The flow of relatively hot leakage air through the servomechanism helps to prevent sticking of the throttle valve during low temperature operation, and the bleed system utilized precludes the necessity of connecting an additional high pressure control line to the pilot valve.

It is, therefore, an object of the present invention to provide an improved turbine speed control system.

Another object of the invention is to provide a rotary speed control system for a fluid motor embodying improved damping means for preventing oscillations about the set or desired speed.

A further object of the invention is to provide a turbine speed control system including a sensing unit operatively connected to the turbine and a servomechanism for translating change signals from the sensing unit into changes in fluid inlet flow to retain the turbine at a constant set speed.

Still another object of the present invention is to provide a fluid motor speed control system having a minimum of inherent hysteresis in the operating portions thereof to impart a maximum of sensitivity and accuracy in the speed control. a

A still further object of the invention is to provide im proved flyweight mechanism for sensing changes in rotary speed of the fluid motor.

An additional object of the invention is to provide an improved sensing unit in a turbine speed control system, eliminating the need for a rotating seal between a flyweight portion and a pilot valve portion.

An important object of this invention is the provision of improved and simplified damping means in a fluid motor rotary speed control system to substantially eliminate hunting about the set speed.

Other objects, features and advantages of this invention will be apparent from the following detailed description of two embodiments, by way of preferred examples Patented Feb. 18, 1958,

only, taken in conjunction with the accompanying drawings.

On the drawings:

Figure 1 is a schematic, partially sectional view of a turbine speed control system according to the present invention;

Figure 2 is a longitudinal sectional view of a speed sensing unit shown schematically in Figure 1;

Figure 3 is a longitudinal sectional view of a second embodiment of a speed sensing unit;

Figure 4 is a diagrammatic view similar to Figure l but showing the turbine speed control system utilizing a sensing unit as shown in Figure 3;

Figure 5 is a sectional view of a servomechanism as shown in Figure 1.

As shown on the drawings:

In Figure 1 is illustrated a fluid motor or turbine rotary speed control system including a sensing unit assembly 11 and a servocontrol or servomechanism assembly 12 for controlling the speed of a turbine 13. The sensing unit 11 includes a fiyweight governor portion 14 and a pilot valve portion 15a with the fiyweight por tion connected for rotation through the turbine and converting centrifugal translation of the fiyweights to axial translation of the pilot valve. The servomechanism 12 includes control means 16 and damping means 17 operatively associated with a throttle valve 18 controlling a variable orifice 19 connecting a fluid supply line 20 to a turbine supply line 21. The turbine 13 is drivingly connected to a working mechanism 22 such as an aircraft booster pump.

For supplying high pressure fluid to the servomechanism 12 a pair of bleed lines 24 and 25 are connected,'respectively, from the high pressure supply line 20 to a control chamber A and a control chamber B. High fluid pressure in the chamber A coacts with the control means 16 to bias the throttle valve 18 toward open position of the variable orifice 19 while high pressure in the chamber B coacts with the control means 16 in a reverse manner to close the variable orifice 19. A pair of orifices or restrictions 26 and 27 are provided in the bleed lines 24 and 25 respectively, to restrict flow into the chambers A and B to induce a pressure drop in response to fiuid flow.

For connecting the servo control chambers A and B to a pair of ports 28 and 29 in the sensing unit 11, interconnect reference lines 30 and 31 are respectively provided. An ambient pressure reference line 32 connects the sensing unit 11 to the ambient air through a pilot port 33. In the neutral position shown in Figure 1, a pilot valve 15a closes ,both of the ports 28 and 29. However, when the valve 15a is biased to the right, the port 28 is connected to the ambient air through the passage 32, and when the valve 15 is biased to the left, the port 29' is connected to the ambient air through the passage 32. Referencing the port 28 to the ambient atmospheric air produces a flow from the supply line 29 through the chamber A and the sensing unit 11. The consequent pressure drop through the orifice 26 reduces the pressure in the chamber A to bias the throttle valve 18 toward closing position of the variable orifice 19 responsive to the higher pressure in the chamber B. When the port 29 is referenced to ambient air, the pressure in the chamber B is lowered in a similar manner to bias the throttle valve 18 toward open position relative to the variable orifice 19 in response to the higher pressure in the chamber A.

The damping means 17 divide another portionof the schematically shown servomechanism 12 of Fig. 1 into'a damping chamber C and a chamber D referenced to ambient pressure through a port or opening 34. The damping chamber C is referenced to turbine upstream. pressure by means of a reference line 35 connected to the turbine supply line 21.

High pressures in the chamberv C augment action of the pressure in chamber B to bias the throttle valve 18 toward orifice closing position.

Referring to Figure 2, one preferred embodiment of the sensing unit assembly 11 is shown in longitudinal cross-section. The fiyweight governor portion 14 of the sensing unit 11 comprises a rotor assembly 36 for biasing an axial shaft 37 to the right and compression biasing means in the form of a compression spring 38 for biasing the shaft 37 towards the left as shown in the drawings. The rotor assembly 36 includes a rotor casing 39 having an internally slanted wall portion 40 diverging toward the right with a pair of flyweights 41 adapted for traveling thereon. The flyweights 41 are rotatably connected to the end portions of arms 42 by means of pins 44, and the arms 42 are pivotally connected at their other end portions to a transverse member 45 by means of pins 46. The transverse member 45 is fixedly attached to the shaft 37 within the casing 39.

For rotatably supporting the rotor assembly 36 Within the sensing unit 11 an anti-friction bearing 47 has its outer race attached within a cylindrical casing portion 48 of the sensing unit and an inner race fixedly attached to a sleeve support portion 49 of the rotor assembly. The sleeve support portion 49 has an annular rim 50 abutted against an annular shoulder 51 of the rotor casing 39 and retained thereagainst by means of a snap ring 52 to fixedly connect the casing 39 to the sleeve support portion 49.

For slidably supporting the left end portion of the shaft 37 within the rotor assembly 36 a bushing 54 is fixedly attached within the rotor casing 39 and has a central bore 55 receiving the left end portion of the shaft 37 in slidable relation therein. For slidably supporting the right end portion of the shaft 37 within the rotor assembly 36, a sleeve 56 fixedly retained Within the sleeve support portion 49 and has an axial bore 57 therethrough containing bearings 58, which, in turn, support the shaft 37 in slidable relation relative to the rotor sleeve support portion.

For controlling the pressures within the chambers A and B of the servomechanism 12 the pilot valve 15a of the pilot valve portion 15 is slidably disposed in a pilot valve casing 59 which is fixedly secured in coaxial relation relative to the casing 48 by means of an annular-engagement portion 60 engaged in an axial end bore 61 formed at the right end of the casing 48. To retain the valve casing 59 in fixed coaxial relation relative to the casing 48 bolts 62 are inserted through an external flange of a cap 64 and have externally threade'd'end portions 65 in threaded engagement in an external "flange formed on the casing 48. The cap 64 has an annular end groove 66 receiving an annular engagement portion 67 at the end of the valve casing 59 opposite to the engagement portion 60. Thus, the valve casing 59 is fixedly clamped between the casing 48 and the cap 64, all three of these portions forming the outer body of the sensing unit 11.

In order to retainthe anti-friction bearing 47 within the casing 48 an annular spacer 68 is inserted within the bore of the casing 48 with its left end abutting the outer race of the bearing 47 and its right end pressed axially inwardly by the annular engagement portion 60 of the valve casing 59. An inwardly ofiset right end portion 69 of the spacer sleeve 68 forms an annular groove 70 which coacts with the defining'wall of the casing bore 61 to receive a sealing ring 71 of suitable resilient sealing material.

The pilot valve 15a is slidably received in a sleeve member 72 which is fixedly disposed in an axial bore 74 of the valve casing 59 by means of an end flange 75 of the sleeve abutting an annular shoulder at one end of the bore 74 and a snap ring 77 engaging the flanged end of the sleeve 72 and the valve casing 59.

To provide means for controlling fluid flow through the pilot valve portion 15 three spaced annular grooves 78, 79 and 80' are formed in the surface of the bore 74 and communicate with the interior of the sleeve 72 by means of apertures 81, 82 and 84, respectively. A pair of raised annular portions 85 and 86 are formed on the valve and are connected by means of a reduced diameter stem 87. When the valve 15 is in the neutral position, the raised portions 85 and 86 close the apertures 81 and 84, respectively. When the valve 15a is displaced to the left as shown in Figure 2, communication is afforded between apertures 81 and 82, and when the valve 15a is displaced to the right, communication is afforded between apertures 82 and 84. The port 29, shown schematically in Figure 1, provides communication between the annular groove 78 and the exterior of the pilot valve casing 59. As shown in Fig. 2 the port 29 is provided with a tapered, internally threaded nipple engagement portion 88. The port 33, shown schematically in Figure 1 communicates with the annular groove 79, and is provided with an internally threaded nipple engagement portion 89. The port 28, shown schematically in Figure 1, is not shown in Figure 2 but is formed similarly to the ports 29 and 33 and communicates with the annular groove 80.

In order to reciprocate the valve 15a in response to axial movement of the rotor shaft 37, a bearing retainer abutment 90 is provided at the right end of the shaft 37 and retains the outer race of an anti-friction bearing 91 in fixed relation therein. The inner race of the bearing 91 is retained in fixed relation on a reduced diameter end stern portion 92 formed on the right end portion of the shaft 37.

To seal the interior of the casing 48 from the interior of the pilot valve casing 59, a flexible diaphragm 94 is clamped around its outer peripheral portion between the right end of the sleeve 68 and the left end of the pilot casing 59. The bearing retainer 90 abuts the central portion of the left face of the diaphragm 94, and a radial flange 95 formed on the left end of the valve 15 abuts the opposite face of the diaphragm so that the central portion of the diaphragm is clamped between the bearing retainer 90 and the valve 15, without necessitating puncturing of the diaphragm, to eliminate possible sources of leakage.

Thus, the shaft 37 and the rotor assembly 36 may rotate freely with respect to the casing 48 and the valve 15a without rotating the valve while still imparting axial displacement to the valve in response to axial movement of the shaft 37.

For sealing the interior of the pilot casing 59 from the interior of the cap 64 a second diaphragm 96 is clamped along its outer peripheral portion between the axially abutting surfaces of the casing and the cap. A radial flange 97 is fixedly secured at the right end of the valve 15 and abuts the central portion of the left face of the diaphragm 96. Opposing the flange 97 on the opposite side of the diaphragm 96 is a radial flange 98 formed on the left end of a spring retainer sleeve 99. A shank portion 100 of the sleeve 99 is encircled by the compression spring 38, and the left end of the spring 38 abuts the axially inward surface of the flange 98 to urge the sleeve 99 to the left to firmly clamp the diaphragms 94 and 96 at their central portions and to provide a biasing force toward the left to oppose the biasing force imposed by action of the flyweights 41 when the rotor assembly 36 is rotated.

In order to restrain movement of the right end of the spring 33 and to close an internally threaded bore 101 in the cap 64, a retainer cover 102 has an externally threaded shank portion 104 threadedly inserted into the bore 101. A wrench engagement flange 105 is provided at the right end of the retainer cover 102 to enable insertion and removal of the same.

For guiding the spring retainer sleeve 99 and the spring 38, a sleeve guide 106 has a radial flange 108 bottomed in an axial bore 107 formed in the threaded shank 104 of the retainer cover 102 and opening into the interior of the cap 64. An integral axial shaft 109 is dis.-

posed in conforming slidable relation within the central bore of the retainer sleeve 99.

Means are provided for preloading the compression spring 38 in order to adjust the control speed setting at which the sensing unit 11 controls the rotary speed of the turbine 13. Herein such means comprise preload washers 110 (herein shown as one). Any number of washers 110 may be inserted between the flange 108 and the right end of the spring 38 in order to vary the initial compression of the spring over a wide range.

For coupling the rotor assembly 36 to the turbine 13 a drive spline 111 is provided at the left end portion of the rotor casing 39. The drive spline 111 is inserted in a mating splined aperture (not shown) in a rotor drive portion of the turbine 13.

In order that the opposed faces of the diaphragms 94 and 96 be exposed to the same biasing pressure in order not to upset the centrifugally controlled operation of the valve 15a, a pair of ambient pressure reference passages 112 are formed from the port 33, which is referenced to ambient pressure, to the opposite ends of the pilot valve casing 59. These passages 112 also insure that any axial leakage past the annular raised poritons 85 and 86 of the valve 15a'Will be vented to the atmosphere.

The interior of the casing 48 is open to the gear case (not shown) of the turbine 13 in order to obtain lubrication for the bearings 47 and 91. However, the gear case of the turbine is maintained at substantially sea level pressure, so that a biasing force is applied to the diaphragm 94 when the ambient atmospheric pressure is different from standard seal level pressure. Hence, a vent port 114 is provided in the cap 64 to communicate with theinterior thereof. This vent port 114 is also vented to the turbine gear case in order that an equal and opposite biasing force be applied to the right face of the diaphragm 96 to balance the force applied tothe left face of the diaphragm 94. Therefore, the sensing unit 11 is entirely free from any net pressure bias in either axial direction.

To provide a connection to one end of a duct (not shown) connecting the interior of the cap 64 to the interior of the turbine gear case, an internally threaded tapered portion 115 is provided in the vent port 114 in a manner similar to the internal threading of the ports 29 and 33.

An alternative embodiment of a sensingunit assembly is shown in Figure 3 and designated by the reference numeral 120. The sensing unit comprises a rotor,

casing 121 and a valve casing 122 adapted to be held in fixed abutted relation by means of bolts (not shown) in attachment flanges 124 and 125 formed on the rotor casing and the valve casing, respectively. A sealing ring 126 is provided between the abutted casings and is disposed in an annular groove 127 at the left end of the valve casing 122.

A rotor assembly 128 having slanted surfaces 129 therein and'a flyweight unit 130 cooperating therewith, as explained in connection with sensing unit assembly 11, is rotatably supported Within the rotor casing 121 by means of an anti-friction bearing assembly 131. The rotor assembly 128 includes a forward casing member 132 having the slanted surfaces 129 therein and provided with an attachment spline 134 at the left end thereof. A rearward bearing sleeve support portion 135 of the rotor assembly is fixedly attached to the forward portion 132 by means of screws 136 and has a tubular support portion 137 supporting a sleeve 138 therein. The sleeve 138 retains shaft support bearings 139 for slidably supporting a rotor shaft 140 at the right end portion thereof. For slidably supporting the left end portion of the shaft 140 a bushing 141 is provided.

In order to retain the inner race of the bearing 131 in fixed position on the rotor assembly 128 the right end portion of the sleeve support 135 is externally threaded to receive a nut 142 which urges the inner race of the bearing against an annular shoulder 144 formed on the sleeve' support izs. A lcek waslie'r 1451's disposed -l$-- tween the bearing 131 and the nut-142--andhas lock" tabs 146iand2147 contafzied' iii a peripheral gro'ove 148 of the nut142 and -a keyvvay slot Bi -formed iii thetuhfilar portion 137,.respe'ctivelyi a r ,For: retaining the outer race of the bea'ririg'131 in fixed relation relative to the rotor casing-121,a retainer sleeve 150. is, provided withinthe interiorof the-casings 121 and7122 andis. formed'with' an annular groove 151' receiving the inward portion of-thesealing ring-126 to further insure a good. seal. Between "the: abutted casing 121 and 122; The left endof thesleevez150 abuts .the outer race of the bearing 131 to urge thesame'i against a retaining ring rl52 formed integrally Within the..casing:121.

Means are provided for sealing theiinterior of: the casings 121an'd 122" containing; the rotor assembly. 128 from the interioreof the -casings1122to the right. of the rotor: Herein such'means comprise ai-deflectableun perforated; diaphragm 154 having its, outer peripheral portion retained against anannular shoulder. 155 provided in the interiorofthe'valve casing 122 by the right endof the'sleeve 15i); Thecentral portion of the diaphragm 154' is clamped between a bearing retainer abutment 156 against the left face thereof and aradial flange 157 of apilot valvet158 against'the right facethereof.

The bearing retainer 156 is fixedly retained on the outer face of:an-anthfrictionbetiring:159. The inner race of the bearing 159- i's-retained' on a' retainer :bushing 150 which is, in turn, retained on a reduced diameter right end portion 161: of the shaftil ill. v Thus, the rotor assembly 128 isrotatably mountedawithiir the sensing unit 120 and'arrangedtoimpart axial movement to' the pilot valve 158-without rotation thereof and without the neces sityof providing holes or apertures through theiseal'ing diaphragm 154.

.An elongated valvesleeve 162 isretained within a mating bore 163 through-the valve casing 122'. Anenlarged threaded-portion 165 is threadedly inserted into a mating internally threaded counterbore 166 to the right of the bore 163. A wrenchreceiving:portion 167 is provided at the right end of the valve sleeve 1'62for inserting and-removing the same.

Three annular grooves 163, 169 and 170are formed in the surface of the bore 163 and-cornmunicate with the interior of the sleeve 162 by means of apertures 171, 172 and 174, respectively.

vA port 175-is providediin the'valve'casing 122 and communicates with the. interior 'of the: sleeve lira-through the groove168-and the apertures 1'71, and'a port11'76 communicates-With the interior of the sleeve through the groove r170 and the aperturest174. A. similar port, communicatingwith the interior of the sleeve 162- through. the grooves 169- and the apertures 172, is not shown. Radially raised portions- 177' and 178, .connectediby a reduced diameter stem portion 179 are provided on the pilot valve 158 and-cooperatetwith the' apertures through the sleeve 162-as described in. connection With-the sensing unit 11 as shown in Figure 2 to alternately connect the outer series of apertures 171 and 174 with the center series 172 in accordance: with the position of the valve.

When the valve 158 is in theposition shownin' Figure 3, the apertures 174 communicate with the atmosphere through an axial vent 180. When the valve li isbiased to therightbeyond the neutral position, the apertures 171 communicate with atmosphere through an aperture 181 provided in the left end portion of the sleeve 162 and a vent aperture l z provided through the left end portion of'th'e valve-casing 122. V

In order to bias the-pilot valve 16% toward the left to oppose the bias'of' the rot'orass'emblyilii imposed by the, axial centrifugal force component of the fiyweight unit 136, a compression vspring-164 is=dispsed between the rightfaceof theflange'lso-and the-bottomofa spring" in peripheral conforming relation in the bore.

8 r te m similar tbj' thatflshownin Figure 1 but utilizing the sensing unitf'assen'ibly '120inplace ofthe'sensirlg' unit assembly 11. 'Allisimilar portionsofthefigurare nurnjberedr'wifh the salrrre"n limerals use'd in'Figure I; It will benotd thatthe'bleed lines 26'and27 have been'elimina'ted resultinginaf'niodified'servomechanisinc12a. A high pressurebleediline. I84 extendsfro'rn'the high pressure source Iine'ZlYtOaport '185' which is connected to the annular groove. 16 9.show'n in Figure 3. It will also be noted that'tlfe'positions'of'the lines 30 and 3l have been reversed in their connection to" the pilot valve and are shown as connected topo'rts and 176, respectively. The control system shown in, Figure 4 operates'in a similarmafinerfto that shown-in Figure l except that the high pressure bleedfluidfirstpasses through the sensing unit 120 to be ultimately referenced to the chamber A or the chamber B, depending on whether the turbine 13 is underspeeding or overspeeding, respectively. When one of thevch'ambers- A or B is referenced to the highpressur source; the other chamber-is referenced to the ambient atmospheric pressure through the port 182 or port so that the variable orifice 19 is opened or closed by movement of the throttlevalve 18. The damping or feed back system operates through the chambers C and D in the same manner as described in'conncctionwith Figure 1.

In Figure 5 is shown-the servornechanism 12 which comprises a substantially cylindrical casing 186 having axial cavities or recesses 187 and 188 at the opposite ends thereof. A pair of end caps 189 and 190 are fixedly disposed over the endsof the casing l86-to close the recesses187 and 188,-respectively. The caps 189 and 190 contain respective central cavities or recesses 191 and 192. Separating-means in the-form of flexibledi aphragms194 and 195have their 'rcspective'outer peripheral porti'ensclampedbetweemthecasing 186 and the end caps 189 and190; respectively; Thus; the' recesses" 191,192, 187-, and-1 88c form-"separate chambers Coriespondingto-the'chamber's-A; B; ,'and D, re'spectively,' as shown in the schematic drawingsof Figures l and 4;

In order to accommodate: the throttle valve 18 in reciprocablerelation' within the casing- 186 an axial bore 196 is provided therein=for-receiving a valve-sleeve 197 To fixedly retain'the valversleeve l97' within thebore 196, snap rings 193 andl99 are' snapped-into respective annular groovesforrned intthe defining wall ofthebore 196 ai1'd' abutthe opposite faces of the sleeve. The throttle valve valve-skirt 261 and nead zozware' disposed 'in conforming slidable' 'relation 'With-inthe valve sleeve I97 and have" annular sealing grooves 205 ream-ea thereon, to guardagainst leakagepastthe he'ads.

In order to'operatively"connct' thevalve body portion 2% to thedi'aphragiiis'194 'ar1d 1W5, an elongated axial rod portion lilo-of the throttle valve 18 is fixedly disposed in an axial-bore 26W formed'through the reduced diam-' eter stem 294. Clamping plates ZlBS are clamped against the opposite surfaces or the central portions of the diaphragms '19 land195 by meansof nuts 2%)? threadedly in'sertdoverthreaded rod endportions 219 which extend through the -clampingplates and the diaphragms at both ends of news 266 The 'axiallyinw'ard clamping plates 208- ateach end of therodZiltS abut annular shoulders 211 formed at each end of the rod "to oppose the action The reference or'bleed passages": 24 aird25i shown schematibally'in figure 1 are incorporated; as bores ex -V tending axially from a high pressure'inlet' port 212 which is'arl'a'p'ted for connectforeto p'rssufesupply line .shown in Figures 1 and 4. The restrictions 26 and 27 are formed reduced diameter bores in the passages 24 and 25, respectively. It will be understood that in the servomechanism 12a shown in Fig. 4 the bleed passages 24 and -25 are either plugged or not formed.

Means are' provided for forming the variable orifice 19 inconnection with the head 2.02 of the throttle valve 18. In the present instance such means comprises a plurality of radial apertures .214 through the valve sleeve 197 and communicating with thejinlet port'212 by means of a groove 215 formed in the wall-of the bore 196 and registering with the apertures 214; An outlet 'port21-6 is formed in axially offset'relation to the prt21i2-in the side wall of the servomechanism casing 186 and is adapted for connecting to the turbine inlet supply line '21 shown I in the schematic drawings. The outlet port 216 communicates with the interior of the sleeve 197 by means of a groove 217 formed'in the wall of the bore :196 and registering with apertures 218 formed through'va'lvesleeve 197.

The turbine inlet reference pressure pressure line 35 is provided in the form of an axial bore communicating between the chamber C and the outlet port 216.

The ambient pressure reference port 34 is shown as a radially formed bore communicating withchamber D.

In order to providea'connection between the pressure reference lines 30 and 31, as shown in Figures 1 and 4, with the chambers A and B of the servomechanism 12 shown in Figure 5, radially extending'ports 219 and 220 are provided, respectively. The ports 219 and 220 may be internally --threaded-as shownat 221 and 222 for-receiving attachment nipples (not shown).

Sealing means are provided at each side of the groove 215 between-thesurface of the bore 196 and the opposing surface of the valve sleeve 197. The sealing meansare herein shown as a pair 'of resilient sealing rings 224 and 225 disposed in annular grooves formed in the surface of the bore 196 and abutting the opposed surface ofxthe sleeve 19 7.

Reviewing the operation of the turbine speed control system shown in the schematic'drawings'in the light of the detailed Figures 2, 3 and '5, fluid'is conducted from l'the'high pressure source'through'th'e supply'line 20'and enters the servomechanism 12 at the inlet port 212.

I Irr'the embodiment shown in Figure :1 a portion -of the'fiuid passes through the bleed passages 24 aud25 through theorifices 26 and 27 to the chambers A and B. Through the passages 30 and 31, the'fluid is conducted from the chambers A and B into the pilot valve portion 15'of the sensing unit'11 through the ports 28 and 2 9. 'Fromhere the fluid is'rnetere'd through either the apertures '81 or the apertures 84, or is blocked from passing thro h e ther t of ap tures, ep n pon the p siof the orifices 26or 27 to lower the pressure in either the chamber A or chamber B, to result in axial movement of the throttle valve 18 to vary the effective area of the variable orifice 19. Thus, the turbine inlet flow and the pressure in the turbine supply line 21 is controlled by the position of the throttle valve and the amount of pressure "in the supply line. Pressures in chambers A,

B and 'Cproduce forces which are balanced when speed correct and produce forces-which are unbalanced resulting in valve position change when speed is not correct. Sinc he speed 0t th'e'tu bine i a functi at th Pressure drop across the valve and-the flow therethroughrthe' speed of the turbine .will consequently be controlled.

In the system illustrated in Figure-4 the high pressure fluid from the supplysource enters the servomechanism the bleed line 184 is provided for conducting high prestion ofthe'pilot valve'lsa. The position of the pilot sure fluid to the sensing unit through the port 185.

Depending-'-uponthe position of the pilot valve 158 the fluid is either prevented from passingfurther or is metered through either-the apertures 171 or the apertures 174 to be conducted to either the chamber A or thechamber B throughlthelines 3001 31 When one set of apertures 171 or 174 is-opento high pressure, the otherset of apertures :is referenced to ambient pressure'through either the port =18!) or the aperture/18,1 and the port 182, so that the throt le valve 18 is movedin accordance with the position of the pilot valve 158 tovary the size of the variable orifice 19, Since the position of the pilot valve 158 is determined by the speed of the turbine 13 through the rotor assembly in-the same manner as described in connectionwith the first system, the inlet pressure and new into the turbiue- 13 willbecontrolled to control the rotational speed of the turbine.

In bother" the systems, the damping or feed back systerns operatein the samemanner. Fluid pressure downstream of the variable-orifice 19 is referenced to the chamber-C through the reference passage 35, to impose-a closing :bias onlthe throttle valve 18 through the diaphra'gm 194 and the rod 206. This bias is opposedby the pressure in thechamber A and the ambient pressure .in chamber ID and is augmented by the pressure in chamber B, When, for example, a heavy load' is suddenly removed from .the turbine 13, the rateof increase i iturbine speed is high and a correspondingrapid change in throttle val've position is required. The pilot --valve will move to cause the throttle valve to snap, toward closed position as describedabove so-that the pressure in the chamber C willbe lowered and-the resistance to openfing movement of the throttle valve when' set speed is again reached will be reduced; t-hus' substantially 4 decreasingthe time required for recovery from the abnorrnal changein loading of the turbine. The reverse oetttu's when a heavy load is suddenly applied to the turbine; It should be noted that the effectiveness of chamber ;C-;isa function of the rate of change-of the turbine inlet pressure so that a form of rate controlled damping or-feed back is introduced into the system-in order to maintain stability even during rapid changesofloadingontheturbine.

Because of theparticularefiectiveness of the darnping' or feed back system inconjunction with the other-features of the two systems described,- it has been-determined by. test that the speed of the turbinetcan be controlled within an error range. of less than 3%. It hasalso, been found 'by test that the turbine will attain-set speed after only one .or two Oscillations of a magnitude of less-than 5% of set speed when the unit is started from a'standstill.

From the. above description, it will be understood that the present inventi n provides a turbine speed control system which is substantially. simplified, including improved damping vmeans to substantiallyprevent oscillationsin speed about the set or desired speed. The control system accurately and quickly compensates for variations in both air inlet pressure and temperature, and in cost of prod uction of the various com onents.

It l b under to tha m difi i ns and variatiens m yb -eff te i h u eparting tram the scope of the 'novel' concepts of the presentinv'ention.

i1 We claim as our invention: 1. A prime mover system comprising a fluid propelled motor, a source of pressure fluid, means interconnecting the source of pressure fluid with the motor, a servo mechanism having means therein defining a variable orifice controlling fluid flow to said motor, a sensing unit having a pilot valve therein, fluid pressure responsive means in said servomechanism operatively associated with said variable orifice defining means, fiilid connections between said pilot valve and said pressure responsive means, means in said sensing unit connected for rotation with said fluid motor for controlling the position of said pilot valve in response to the rotary speed of said motor, and fluid pressure responsive damping means vented to fluid pressure between said variable orifice and said motor and rigidly associated with said variable orifice defining means for biasing the same toward closed position whereby the condition of said variable orifice is immediately and directly responsive to large orsmall variations in the motor inlet pressure.

2. A prime mover system comprising a turbine, a source of pressure fluid, means interconnecting the source of pressure fluid with the turbine to drive the same, a turbine speed sensing unit having a centrifugal mechanism therein connected for rotation with said turbine, a pilot valve in said sensing unit operatively associated with said centrifugal mechanism, said centrifugal mechanism controlling the position of said pilot valve in response to the speed of rotation of said turbine, fluid pressure actuated means defining a variable area orifice,

first fluid connections referencing fluid pressure from said pressure source to said pressure actuated means for biasing said orifice defining means in opposing directions,

second fluid connections between said pressure actuated means and said pilot valve for permitting alternate flow therethrough from one of said first fluid connections in response to the position of said pilot valve, restrictions in said first connection for inducing a substantial pressure drop in response to fluid flow, and means for damping the action of said fluid pressure actuated means for guarding against speed oscillations in response to changes in operating conditions said damping means comprising a fluid motor deriving its source of energy from the pressure existing in the conduit between said orifice and said turbine inlet.

3. A prime mover system comprising a turbine, a source of pressure fluid, means interconnecting the source of pressure fluid with the turbine to drive the same, a turbine speed sensing unit having a centrifugal mecha nism therein connected for rotation with said turbine, a pilot valve in said sensing unit operatively associated with said centrifugal mechanism, said centrifugal mechanism controlling the position of said pilot valve in response to the speed of rotation of said turbine, a servomechanism having fluid pressure actuated means therein defining a variable area orifice, a fluid connection referencing said pressure source to said pilot valve, fluid connections between said pilot valve and said servomechanism for alternately referencing the fluid pressure from said pressure source through said pilot valve to 'said servomechanism for biasing said orifice defining -means in alternately opposite directions in response to 'the position of said pilot valve, said pilot valve referencing 'one of said second mentioned fluid connections to ambient atmospheric pressure when the other of said fluid connections is referenced to said fluid supply source pressure, and fluid pressure means for damping the action of said control system for guarding against speed oscillations in response to changes in operating conditions, said last named means being rigidly connected to said servomechanism for controlling said variable area orifice defining means and being operative in immediate and direct response to the pressure of the fluid leaving said orifice.

4. A prime mover system comprising a fluid propelled motor, a source of pressure fluid, means interconnecting the source of pressure fluid with the motor, a servomechanism comprising a throttle valve movably mounted in said servomechanism for controlling fluid flow therethrough from said pressure source to said motor, diaphragm means connected to said throttle valve, first and second fluid connections referencing fluid pressure from said pressure source to opposite sides of said diaphragm means for biasing said throttle valve in opposite directions, restrictions in said fluid connections for inducing a substantial pressure drop in response to fluid flow therethrough, and a third fluid connection referencing the pressure between said throttle valve and said fluid motor to one side of said diaphragm means for biasing *said throttle valve toward closed position, and means responsive to motor speed to prevent fluid flow in one of said first and second fluid connections while causing flow .means for substantially lowering the pressure of fluid flowing into alternate ones of said two chambers, second means referencing the pressure at the outlet of said throttle valve to another of said chambers to bias said throttle valve toward closing position, and third means referencing ambient atmospheric pressure to the remaining chamber.

6. A servomechanism comprising a valve mounted in said servomechanism for controlling fluid flow therethrough from a pressure source to a load, diaphragm means connected to said valve, means referencing fluid pressure from said source selectively to opposite sides of Said diaphragm means for selectively biasing said valve in opposite directions, and a fluid connection referencing the pressure between said valve and said load to one side of said diaphragm means for biasing said valve toward closed position.

7. A servomechanism comprising a casing having a fluid passage therethrough connecting a pressure source to a load, a throttle valve reciprocably mounted in said casing for controlling flow through said fluid passage, 3.

pair of flexible diaphragms attached at opposite ends of said throttle valve and cooperating with the walls of said casing to define four separate pressure chambers in the casing, means referencing fluid pressure from said source to two of said chambers for selectively biasing said throttle valve in opposite directions, means referencing the pressure of fluid between said throttle valve and said load to another of said chambers to bias said throttle valve toward closing position, and means referencing ambient atmospheric pressure to the remaining chamber.

8. A prime mover system comprising a fluid propelled motor, a source of pressure fluid, means interconnecting the source of pressure fluid withthe motor, a speed sensing unit comprising a casing, said casing having a valve boretherein and three axially spaced radial ports communicating therewith, a pilot valve slidably mounted in said bore and having a pair of spaced radially enlarged, portions connected by a reduced diameter stem, said enlarged portions being the same distance apart as the two outermost portsto block the same when in central position and to permit fluid flow between the middle part andonly one ofthe outermost ports when displaced from central position, spring means biasing said pilot valve in one direction, a rotorassembly rotatablymounted in said casing, means for connecting said rotor to said fluid motor for rotation therewith, a flexible sealing diaphragm in said casing between said rotor assembly and said pilot valve, means rotatably attached to: said rotor assembly and abutting the central portion ofsaid diaphragm to clamp the central portion between themtatable means and one end of said pilot valve, and means in said rotor assembly operable by centrifugal force to urge said rotatable means against said diaphragm to urge said pilot valve against the bias of said spring means.

9. In a turbine speed control system, a speed sensing unit comprising a casing having a rotor. chamber, a valve section with an axial bore therein and a spring compartment, flexible sealing diaphragms in said casing pressure sealing said rotor chamber from said valve section and said valve section from said spring compartment, said valve section having three axially spaced ports therein communicating with said axial bore, a pilot valve slidably disposed in said bore and alternately connecting the middle port with one or the other of the outermost ports in response to reciprocation of the valve, spring means urging the central portion of one of said diaphragms against one end of said pilot valve and biasing said pilot valve in one direction to urge the other end against the central portion of the other diaphragm, centrifugal rotor mechanism rotatably mounted in said rotor chamber and connected for rotation with said turbine, means rotatably attached to said centrifugal mechanism and abutting the central portion of said other diaphragm on the side opposite to said other'end of the pilot valve, means in said centrifugal mechanism to urge said rotatable means against said other diaphragm to urge said pilot valve against the bias of said spring means, an interconnect passage between said rotor chamber and said spring compartment to equalize the pressures therein, and a by-pass passage in said valve section to equalize the pressures against the opposed faces of said diaphragms.

10. A prime mover system comprising a fluid propelled turbine, a source of pressure fluid, means interconnecting the source of pressure fluid with the turbine, a turbine speed sensing unit comprising a casing having a rotor chamber and a valve section, a flexible sealing diaphragm between said chamber and said valve section, said valve section having an axial bore therein with three axially spaced radial ports communicating with the bore, a pilot valve slidably disposed in said bore and alternately fluid connecting the middle port with one or the other of'the outermost ports in response to reciprocation of the valve, fluid connection means referenced to ambient atmospheric pressure, said pilot valve referencing said connection means to one of said outermost ports when the other of said ports is fluid connected with said middle port, a centrifugal rotor mechanism rotatably mounted in said rotor chamber and connected for rotation with said turbine, means rotatably attached to said centrifugal mechanism and abutting the central portion of said diaphragm to clamp the diaphragm central portion between said rotatable means and one end of said pilot valve, means in said centrifugal mechanism to urge said rotatable means against said diaphragm to urge said pilot valve in one direction in response to increasing centrifugal force, and spring means opposing the bias of said centrifugal means.

11. In a speed control system for a turbine propelled by fluid from a pressure source, a speed sensing unit comprising a casing, a centrifugal rotor assembly in said casing, an anti-friction bearing. rotatably supporting said rotor assembly in .said casing, a shaft reciprocablymounted in said rotor assembly, diverging inner walls formed at one section of said rotor assembly, arms pivotally mounted on said shaft, flyweights rotatably mounted at the outer end portions of said arms and adapted to travel along said diverging walls, whereby centrifugal force induced by rotation of said rotor as- 'semblymoves said shaft. axially by movement of-said flyweights along said diverging walls, an anti-friction bearing mounted on! theoutward end portion of said shaft, a retainer rotatably supported: on said shaft and on said shaft anti-friction bearing, said casing having a valve bore in: one portion thereof with a plurality of ports communicating therewith, a pilot valve slidably disposedin said bore and alternately connecting diflerent ports in response tov reciprocation thereof, a flexible sealing diaphragm between said rotor assembly and said pilot valveand having its, central portion clamped between said retainer and one 'endof said pilot valve, and biasing means urging said pilot valve: in opposition to the movement induced by'rotation o-fsaid rotor assembly.

12. A prime mover system comprising afluid propelled motor, a source of pressure fluid, means interconnecting the source of pressure fluid :withthe motor, a valve housing and valve core defining a variable orifice controlling fluid flow from the pressure source to the motor and speed sensing means controlling saidvalve core, the improvement comprising a diaphragm insaid control mechanism and rigidly connected to said core for biasing said orifice defining core into a valve-closed condition, first means referencing the fluid pressure between the variable orifice and the fluid motor against said-diaphragm to bias the orifice defining core toward orifice; closing position,and means referencing said pressure source against said core to oppose the bias of said first referencing means upon a decrease in motor speed and to aid said first referencing means upon an'increase. in motor speed.

13. A speed control system for a rotaryfluid motor propelled by fluid from a pressure source comprising a servomechanism having means therein defining a variable orifice. controlling fluid flow to said; motor, a sensing unit having a pilot valve therein, fluid pressure responsive means in said servomechanism operatively associated with said variable orifice defining means, fluid connections between said pilot valve and said pressure responsive means for selectively biasing said pressure responsive means in opposite directions, a fluid connection between said pilot valve and said fluid pressure source, means in said sensing unit connected for rotation with said fluid motor for controlling the position of said pilot valve in response to the rotary speed of said motor, and fluid pressure responsive damping motor means vented on one side thereof to fluid pressure between said variable orifice and said motor and vented on the other side thereof to a substantially constant lower pressure, said damping motor means being positively interconnected with said variable orifice defining means for biasing the same toward closed position upon an increase in fluid pressure between said variable orifice and said motor.

14. In a speed control system for a fluid motor includ ing fluid pressure responsive means defining a variable orifice controlling fluid flow from a pressure source to the motor and speed sensing means controlling said pressure responsive means, the improvement of damping means comprising a diaphragm mechanism in said control system and connected rigidly to said orifice defining means, means referencing the fluid pressure between the variable orifice and the fluid motor against said diaphragm mechanism to bias the orifice defining means toward closing position upon an increase in said last named pressure, and means referencing ambient atmospheric pressure against said diaphragm mechanism to oppose the bias of said first referencing means.

15. In a speed control system for a fluid motor propelled by fluid from a pressure source, a servomechanism comprising a throttle valve mounted in said servomechanism for controlling fluid flow therethrough from said pressure source to said motor, diaphragm means connected to said throttle valve, means referencing fluid pressure to opposite sides of said diaphragm means for biasing said throttle valve in opposite directions,rneans 15 for venting the pressure on one or the'other sides of said diaphragm in response to motor speed fluctuations, and a fluid connection referencing the pressure between said throttle valve and said fluid motor to one side of said diaphragm means for biasing said throttle valve toward closed position.

16. In a speed control system for a fluid motor propelled by fluid from a pressure source and including a speed sensing pressure control unit fluid connected to said pressure source, a servomechanism comprising a casing having a fluid passage therethrough pressure connecting said pressure source to said fluid motor, a throttle valve reciprocably mounted in said casing for controlling flow through said fluid passage, a pair of flexible diaphragms attached at opposite ends of said throttle valve and cooperating with the walls of said casing to define four separate pressure chambers in the casing, means referencing fluid pressure from said speed sensing unit to two of said chambers for biasing said throttle valve in opposite directions, means referencing the pressure of fluid between said throttle valve and said fluid motor to another of said chambers to bias said throttle valve toward closing position, and means referencing ambient atmospheric pressure to the remaining chamber.

17. A speed control system for a rotary fluid motor propelled by fluid from a pressure source comprising a throttle valve controlling flow through a conduit extending from said pressure source to said fluid motor, a servomechanism controlling said throttle valve, a pilot valve controlling said servomechanism, speed sensing means operatively associated with said fluid motorpand controlling said pilot valve in response to the speed of rotation of said motor, and a feedback damping system including a second pressure actuated servomechanism secured to said throttle valve and a pressure connection referencing the fluid pressure in said conduit between said motor and said throttle valve to one side of said second pressure actuated servomechanism to bias said servomechanism and said throttle valve toward closed position, and means applying a substantially constant lowerpressure to the opposite side of said servomechamsm.

References Cited in the file of this patent UNITED STATES PATENTS 936,261 Warren Oct. 5, 1909 1,063,547 Kieser June 3, 1913 1,063,548 Kieser June 3, 1913 1,319,463 I Doble Oct. 21, 1919 1,411,412 Converse Apr. 4, 1922 1,464,749, Dahlstran Aug. 14, 1923 1,516,011 Heath Nov. 18, 1924 1,741,489 Watts Dec. 31, 1929 1,910,322 Coflin etal May 23, 1933 1,995,885 Gutermuth Mar. 26, 1935 2,020,847 Mitereff Nov. 12, 1935 2,197,171 Annin Apr. 16, 1940 2,208,539 Brown July 16, 1940 2,219,359 Goit et a1. Oct. 29, 1940 2,230,914 'Sherman Feb. 4, 1941 2,237,780 Gottlieb Apr. 8, 1941 2,332,910 Gottlieb Oct. 26, 1943 2,342,763 Smith Feb. 29, 1944 2,364,817 Reggio Dec. 12, 1944 2,365,650 Shaw et al Dec. 19, 1944 2,485,514 Sturrok Oct. 18, 1949 FOREIGN PATENTS 27,022 Great Britain 1911 402,852 Italy Mar. 26, 1943 

